There is a visible, evolving struggle in U.S. media stories over how to discuss climate change and weather, particularly extreme weather events. [1] Many news stories have long separated climate change and weather as separate entities, often bringing them together only during an “extreme” event to ask if there is definitive causation between them — i.e. did climate change cause a particular extreme weather event? This question is then usually posed to scientists with the expectation of a definitive yes-or-no answer. Such questions do not readily accommodate the complexity of Earth’s climate or the nature of scientific research. Further, such questions in essence force scientists to pretend there are two realities, one with the “natural,” pre-industrial greenhouse gas levels, and one with the anthropogenically changed levels, and determine whether the latter or the former “caused” the event. It is a misleading question that often traps scientists and confuses the public.

Fortunately, some news stories are beginning to focus on the connections that can be made between anthropogenic changes in atmospheric conditions and daily weather events, aided in part by advances in science. Such articles often either directly or indirectly reframe the question from “did climate change cause this weather event?” toward “how are human-generated emissions affecting physical conditions in ways that can manifest both over the long term (climate) and the short term (weather)?” This article argues that scientists can help further facilitate this development through effective framing and communication. This is important given the politicization of climate change science, where scientific uncertainty is often mischaracterized and promoted as an excuse for inaction. [2]

Reframing the question

To determine an extreme event, scientists provide quantitative definitions of extremes, usually anchored in historical observations. For example, a 30-year record of observations for temperature is described by its mean and how the observations are spread around that mean. The spread is quantified to answer the question: How far is this temperature observation from the mean? The standard deviation is a common measure of the spread, and a logical measure of an extreme event is an event that is one or more standard deviations away from the mean. With this approach, when the scientist is faced with the question of whether or not an extreme event can be attributed to climate change, the question defaults to — is this extreme event more extreme than any previously recorded event? Only with a positive answer to this question is there a potentially convincing yes-or-no attribution of the event to climate change. Otherwise, the scientist intuitively falls to the language of statistics, relying on probability distribution functions, correlated variables, coherence of information from multiple sources, and more sophisticated and precise measures of “extreme.”

Many members of the media and the public, on the other hand, expect a definitive answer of the question “can this event be attributed to climate change?” If for no other reason, such an answer is expected because one of the most publicized attributes of global warming is more frequent or intense extreme weather. [3] Even well-crafted, nuanced responses to this question by scientists, however, can appear in the public realm as uncertainty and equivocation. This perceived equivocation, in turn, can fuel public misunderstandings and political arguments. [4]

While generally not possible to say that a particular event can be absolutely attributed to climate change, asserting that an extreme weather event is not representative of climate change is also false. If climate is described by some measure of the mean weather and the distribution about that mean, then climate change is represented by a change in that mean and change in the distribution of the spread. There will be overlap of similar weather events in both the historical climate and the changed climate. A particular extreme event might very well lie in the distribution of the historic climate and the changed climate, and just because it is in the distribution of the historical climate does not mean it is not typical of the changed climate. That is, weather and climate are different descriptions of the same phenomena, and to make the separation suggested in the above yes-or-no attribution question is a false dichotomy.

Perhaps a more accurate question would be “have anthropogenic emissions changed atmospheric conditions in ways that made this ‘extreme’ event more likely to occur?” or “can we quantify the contribution of anthropogenic warming to the energy budget of a particular event?” Embedded in these questions is likelihood, and there is not a definitive separation of “natural” and “anthropogenically changed” climate. In these cases, the answer is often yes. This positive knowledge needs to be unequivocally communicated to people. It is still a difficult challenge of communication, however, and there is the obvious question — how to influence the conversation so that more scientifically appropriate questions are asked.

Managing Uncertainty

Being able to reframe the discussion to manage uncertainty is increasingly important given the politicization of climate change. The scientific practice of reporting on uncertainty has been seized upon in a now well-documented and apparently deliberate attempt to distort public understanding of climate science and avoid regulation. [5], [6]

In Doubt is Their Product: How Industry’s War on Science Threatens Your Health, Assistant Secretary of Labor for Occupational Safety and Health David Michaels lays out how this effort goes beyond just traditional public relations. [7] It is made up of lawyers, think tanks, researchers, and specialized organizations involved in the shaping of public opinion, scientific research, government regulation, and legal rulings — an operation so sophisticated Michaels considers it an industry of its own, the product defense industry. Journalists and social scientists have researched how fossil fuel companies and their supporters have borrowed the tactic, and some of the same scientists and law firms, as Big Tobacco.[8], [9] The tactic is to demand certainty as the only acceptable standard for action, while simultaneously manufacturing uncertainty, by funding dubious studies or creating false controversies like “Climategate.” [10]

Those pushing this tactic understand that doubt is a powerful way to keep climate change from being identified and seen as a social problem requiring action. Extreme weather events offer easy opportunity to generate doubt, for example, with some news outlets and commentators pointing to snowstorms as “proof” that global warming is false doctrine — as could be seen with “Snowmageddon.” [11] Such anecdotal “proof” that global warming is false is intuitive and appealing. Of course, in this case it ignores that climate models do indeed predict increased precipitation, and hence, large snow events.

The realization that, in the media, climate change is as much a political issue as a scientific issue is consequential. The question about whether climate change caused a particular weather event is a natural question from a journalist. If scientists were to generate an event attribution question, however, it would not be such a yes-or-no question; it is doubtful that peer reviewers would positively review a scientific proposal focused on identifying whether a single weather event was “caused by climate change.” Further, the journalistic question cannot be answered without introducing some description of uncertainty. Even if the question is innocently or earnestly asked, the answer by the scientist in a public forum provides the seed of uncertainty that can be managed by those whose desire is to maintain doubt and question credibility. When the question is posed by someone with a political desire to oppose action on climate change, the question is a classic leading question — it demands a yes-or-no answer with neither yes or no being an attractive answer.

Improving the discussion

Using a simple and common yes-or-no question often asked publicly about extreme events and climate change, we have explored the relation of the question to both the scientific method and the political argument. It is important to realize that there are many agendas being pursued in discussions of climate change, and that the rational pursuit of the reconciliation of a complex body of knowledge with other societal issues is often not the first and foremost agenda. There are a number of strategies for changing and reframing the discussion. Perhaps at the top of the list is the realization that scientists are participants in the discussion; it is not simply a matter of scientists educating and communicating knowledge to a knowledge-seeking public. As a participant in the discussion, scientists do not merely answer questions as posed, but contribute to the definition and framing of questions.

Rather than initiating an answer about yes-no causation with “it is not possible to attribute any single event to climate change,” it is perhaps worth answering instead with a statement that the question disconnects weather and climate, natural and anthropogenically changed, in a way that is not meaningful. Following such a check, there are a number of ways to advance — to develop balance.

One path would be to address the shortcomings of the question. Another path might be to provide an answer about weather and climate that conveys the relationship between them with concrete examples that are likely to be intuitive or become intuitive. Continual, consistent, and direct statements and reaffirmation of information serves to set a knowledge-based context for the foundation of public perceptions of climate change. [12] Rather than answers to questions that frame climate change in terms of complexity and unknowns that prohibit all of us from making definitive statements, it is better to provide answers about what is definitive.

Theory demands and observations confirm that warmer air in the lower atmosphere will hold more water, and hence, have more water and energy available for severe storms. The year 2010 did not just culminate the hottest decade since instrumental climate records began in 1850 — with 18 nations experiencing their hottest ever temperatures — but also the wettest, according to the World Meteorological Organization. [13] Groisman et al. [14] tracked a 14% increase in heavy (top 5%) and 20% increase in very heavy (top 1%) precipitation events in the U.S. over the past 100 years, mainly in spring and summer.

Direct observations reported by the U.S. Global Change Research Program show that weather events measured as extreme have become more frequent in the past half-century and, in the cases that have been studied, the mechanisms are those that one would expect from a warming world. [15] More droughts and heat waves are expected because of hotter, longer-lasting high pressure systems that dry out the land, like the Russia heat wave of 2010. Conversely, more floods are expected because hotter air holds more moisture. When the conditions are “right,” that moisture is released, leading to increased possibility for floods such as the one in Pakistan in 2010, or unusually heavy snowstorms, like the East Coast’s “Snowmageddon.” The “right conditions” will almost certainly be similar to the conditions that were similarly “right” in historical storms, heat waves, droughts, and floods. Hence, they will appear largely consistent with the “natural” climate. Through focused, physics-based diagnostics, however, it is possible to calculate what portion of increased moisture is attributable to trends in warming associated with anthropogenic emissions. [16]

Tying together basic pieces of correlated information from observations, theory, and predictions, helps illustrate the relationship between weather, extreme weather, and climate. It leads to a coherent and convergent message that will ultimately be far more effective and more accurate than saying that weather is not the same as climate. It reveals a body of knowledge that is consistent with both weather and climate change, which is powerfully different from the well known retort that a specific event cannot be attributed to climate change, but that the event is not inconsistent with climate change. This will require a thinking media to generate more scientifically informed reports and questions.

Scientific advances in extreme weather and climate

The demands on the community of scientists by the public and the seriousness of the consequences of global warming to society motivates new scientific ways to determine the degree to which certain extreme weather events can be attributed to human influences. Lawrence Livermore National Laboratory climate researcher Ben Santer suggested using climate models as a “control experiment” for pre-industrial greenhouse gas levels. The goal is to determine how many times an extreme event of a given magnitude should have been observed in the absence of human interference and compare that to present conditions. The result of this quantification is called “fractional attributable risk.” [17]

Stott et al. [18] used the fractional risk method to estimate how much human activities may have increased the probability of occurrence of the 2003 heat wave in Europe, and found it is very likely (confidence level >90%) that over half the risk of European summer temperatures exceeding a threshold of 1.6 K is attributable to human influence on climate.

Two recent papers built upon this work: Win et al. [19] found that human-induced increases in greenhouse gases have contributed to intensification of heavy precipitation events over two-thirds of the Northern Hemisphere, based on a comparison of observed and multi-model simulated changes. Pall et al. [20] used a multi-step, physically based “probabilistic event attribution” framework showing that it is very likely that anthropogenic greenhouse gases substantially increased the risk of flood occurrence in England and Wales in autumn 2000, with nine out of 10 cases increased by more than 20%, and two out of three cases by more than 90%.

The extraordinary heat wave in summer 2010 has motivated a number of attribution studies. Dole et al. [21] investigates whether or not the heat wave could have been anticipated and the extent to which greenhouse gas emissions played a role. Relying on datasets spanning 130 years, archived climate model projections, and model predictions to assess uncertainties, they test whether or not a signal of the role of greenhouse gas emissions has risen above the noise of the natural variability. Based on many specific attributes of the region and the event itself, Dole et al. are unable to extract a signal that they can attribute to anthropogenic trends. Dole et al. do state that, based on results from heat event in other regions, “we may be on the cusp of a period in which the probability of such events increases rapidly, due primarily to the influence of projected increases in greenhouse gas concentrations.”

Focusing on European heat waves, Barriopedro et al. [22] determine that the 2003 and 2010 European heat waves are the hottest of the past 510 years. That is, there have been two 500-year events in the past decade. These heat waves are determined to be more than four standard deviations from the 1970-1999 mean, extreme by any measure. Barriopedro et al. are confident in attributing more moderate heat waves (two to three standard deviations) to changes in a shift of a mean summer temperature, i.e. climate change. The more extreme events they link to enhanced variability, with such variability both consistent with the predictions from climate change models and becoming more likely in the next 40 years. Therefore, a definitive climate-change signal will emerge for these most extreme events.

The methods described above demonstrate scientific advances for assessing the human influence on extreme weather. [23] The different studies focus on the determination of how the intensity or duration of an event is changed due to, for example, the trend in temperature from the increase of greenhouse gases. That is, they do evaluate the event in the context of a changing climate. These studies also build in a link to societal impact by framing their results in terms of risk. They exemplify an evolving field of research and communication that seeks to perform early detection of a global-warming signal emerging from a background of high variability – of high noise. To some scientists there is a consistent story emerging. To others, vested in particular methods and conclusions, there are important differences. The result is that scientific debates that were historically carried out in the slow deliberations of peer-reviewed journals are now on public display [24] and can be misrepresented.

In efforts to communicate outside of the realm of scientific argument, however, it is important for climate scientists to reiterate in public forums that the environment in which weather processes operate has fundamentally altered. It is warmer at the surface, colder in the lower stratosphere, wetter where it should be wetter, with reduced springtime snow cover, increasing sea surface temperatures, and shrinking glaciers; [25] it is an environment where the coherent and consistent signal of global warming due to anthropogenic greenhouse gas is emerging ever more convincingly. Isolating the arguments to individual events and seeking a single smoking gun without consideration of this coherent and convergent picture of the Earth’s climate as a whole are disservices to the body of scientific knowledge and communication of that knowledge. Still, with the presumption that we will continue in this public conversation of event attribution, it is important to remember that it is just as much a fallacy to assert, as some media stories still do, [26] that an extreme weather is not due to climate change — indeed, no extreme weather event can be said to occur outside of anthropogenic climate change.

Why It Matters

Reframing the discussion on climate and weather is important not only for scientists and the media, but for societal understanding and action. Risk perception studies done in the U.S. and U.K. [27] suggest that many people think of climate change as a distant concern, not immediately apparent to them, and thus not a large cause of concern, particularly when compared to more immediate issues in peoples’ lives. Such thinking is further aided by deliberate attempts, particularly in the U.S., to portray climate change science as uncertain and contested. Recent Gallup surveys, for instance, show that there has been a measurable decrease since the 1990s in just how severe much of the U.S. population regards climate change. [28]

This confusion is not helped by the current discussion around climate and weather. Presently we are engaged in an unproductive game where, after an extreme event, there are assertions by scientists and non-scientists that the event is “climate change.” Both the formal and informal media respond with questions about whether those assertions stand up to scientific scrutiny. Almost certainly the answer is no, because as publically posed the question essentially asks scientists to divide the world into two different realities — the natural and the anthropogenically changed — and determine which one provided the conditions that “caused” the event. Indeed, this is a misleading question, as it embodies the climate skeptic’s assertion that there currently exists an alternate, parallel reality in which climate change does not exist.

To improve the discussion, we have argued for initiating and addressing media inquiries regarding weather and climate in ways that make it more difficult for scientific uncertainty to be misrepresented or misunderstood. Specifically, redirecting media questions away from yes-no, weather-climate change, natural-anthropogenically changed dichotomies, and instead highlighting the shortcomings of such a question, opens up space to more meaningfully discuss the relationship between climate change and weather. Even in instances where an event falls within historic natural variability or a human signal cannot be discerned, the reality of widespread anthropogenic changes to our planet still exists, and needs to be communicated and understood.

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